The present invention relates to a novel process for preparing (S)-1-[2(S)-(1,3-dihydro-1,3-dioxo-isoindo-2-yl)-1-oxo-3-phenylpropyl ]-1,2,3,4-tetrahydro-2-pyridine-carboxylic acid methyl ester which is a useful intermediate in the preparation of [4S-[4.alpha., 7.alpha.(R*), 12b.beta.]]-7-[(1-oxo-2(S)-thio-3-phenylpropyl) amino]-1,2,3,4,6,7,8,12b-octahydro-6-oxo-pyrido [2,1-a][2]benzazepine-4-carboxylic acid and [4S-[4.alpha., 7.alpha.(R*), 12b.beta.]]-7-[(1-oxo-2(S)-acetylthio-3-phenylpropyl) amino]-1,2,3,4,6,7,8,12b-octahydro-6-oxo-pyrido[2,1-a][2]benzazepine-4-car boxylic acid and pharmaceutically acceptable salts thereof which are useful as inhibitors of enkephalinase and angiotensin converting enzyme [European Patent Application No. 0 481 522 A1, published Apr. 22, 1992] and to novel intermediates thereof.
The process and intermediates of the present invention provide a novel enantiospecific method for preparing (S)-1-[2(S)-(1,3-dihydro-1,3-dioxo-isoindo-2-yl) -1-oxo-3-phenylpropyl]-1,2,3,4-tetrahydro-2-pyridine-carboxylic acid methyl ester.